The structure and properties of two families of lattice-coherent composites, those based on gamma' Ni3Al and those based on TiA/Ti3Al, are shown to have strong similarities. The coherent system of cubic/tetragonal Y2O3-stabilized ZrO2 is then described, and shown to have strong similarities to the system TiAl/Ti3Al. The phase gamma TiAl(L1(o)) and alpha (2) Ti3Al(DO19) are not cubic, and their anisotropic thermal expansion may lead to ratcheting creep under conditions of thermal cycling.